As a data communication network becomes more and more popular today, a so-called home network where electrical home appliances, computers, and other peripheral units are networked to enable communication among them is becoming widely used in the home. A home network, which allows communication among networked devices to share the data processing function and to transmit and receive contents among them, provides the user with convenience and comfort. It is expected that a home network will become more widely used in future.
As a protocol suitable for the configuration of such a home network, there is known Universal Plug and Play (UPnP). Universal Plug and Play (UPnP) allows the user to easily build a network without complicated operations and allows the user on a networked device to receive the services provided by the connected devices without difficult operations and settings. Another advantages with UPnP are that it does not depend on the OS (Operating System) on a device and that devices can be added easily.
Under UPnP, a definition file conforming to XML (extensible Markup Language) is exchanged among devices for mutual recognition. The overview of UPnP is as follows:
(1) Addressing processing for acquiring its own device ID such as an IP address
(2) Discovery processing for searching for the devices in the network and, upon receiving responses from the devices, acquiring information, such as the device type and the function, included in the responses.
(3) Service request processing for requesting a device to provide a service based on the information acquired by the discovery processing
By executing the processing procedure described above, the services can be provided and received by applying devices connected to the network. A device newly connected to a network can perform the addressing processing described above to acquire the device ID, perform the discovery processing to acquire information on other devices connected to the network and, based on the acquired information, issue a service request to the other devices.
For example, when a user wants to reproduce a content, such as music data and image data stored in a server, on the client side device, the client side transmits an acquisition request to the server to transmit content information stored in the server, for example, various types of content attribute information such as the title or the artist name of a tune or a movie, data compression mode information (ATRAC: adaptive transform acoustic coding, MPEG: moving picture experts group, etc.) and, as necessary, copyright information. This attribute information is called metadata or meta information.
In response to the request from the client, the server transmits metadata (attribute information) of the content, owned by the server, to the client. Based on the metadata acquired from the server, the content information is displayed on a display of the client device according to a predetermined display program. For example, a tune list composed of artist names and titles is displayed on the display. Based on the display information, the user checks or selects a content to be reproduced and transmits a content transmission request to the server. The server receives the content request from the client and, according to the received request, transmits the content to the client, and the client side reproduces the received content.
In this way, a content stored in the server in the home network can be accessed from other devices connected to the network. For example, a device connected based on the UPnP connection that is a simple device connection structure described above can acquire a content. When the content is movie data or music data, a TV set or a player connected as a network connection device enables the user to watch a movie or listen to music.
However, the metadata transmitted and received between devices defined in UPnP, for example, between a server and a client, is uniform, so that in devices having various functions, some metadata received from the server may be insufficient.
For example, in the metadata received from the server, there may exist data which allows update processing such as rewrite, deletion and addition. In a case where, for example, a content list is displayed on the client device based on the metadata received from the server, under the existing UPnP, the transmission processing of data for judging which data is allowed to be rewritten, or which data can be subjected to delete and addition processing is not performed. Therefore, the user is required to perform try-and-error type processing in which the user actually tries executing data input in each data field to thereby execute metadata update processing.
As related art disclosed relating to the processing such as rewrite and addition of the metadata, for example, Patent Document 1 (Japanese Published Application Publication No. 2001-292413) can be cited. In Patent Document 1, there is described a structure in which metadata is written every working step in an image processing system gathering, editing/processing, and storing video/audio in a production company of a news program or the like. For example, while an outside broadcast van is moving to a news coverage site, metadata considered in a planning step is transmitted from a data managing apparatus at a broadcast station to an image pick-up apparatus at the news coverage site, and in a coverage step, metadata automatically generated, in addition to the metadata transmitted from the broadcast station, is recorded on a recording medium. In this manner, there is shown a structure which enables writing processing of various types of metadata in respective steps in a recording and reproducing apparatus, editing apparatus or the like. However, in this related art, there is not shown any means clearly indicating a range in which the update of the metadata, such as rewrite, addition, deletion allowed in respective steps or an apparatus, and the like, is enabled.
Furthermore, the metadata includes various data items such as a title, playing time, and data recording date and time, and a data mode in which input is enabled is defined for each data item; for example, only text data, only numeric data or only integer data can be inputted. In addition, in the case of the numeric data, a range of values that can be inputted may be defined. In the case of the text data, the number of input characters and the like may be defined. However, in the existing UPnP, since notification processing of the data mode in which input is enabled or the like is not performed between the devices at the time of transmitting and receiving the metadata, the try-and-error type processing is needed as in the foregoing.
Moreover, with respect to the server providing the content to the client, a server, such as an image data providing server and an audio data providing server, is often provided for each content that the server can provide. These respective servers own the contents in different data modes. For example, ATRAC3, ATRAC3plus, MPEG1, MPEG2, MPEG4 or the like are exemplified.
Although the client side can acquire the types of contents that the server owns in the discovery processing in UPnP, means for acquiring the details of the data modes is insufficient. Even if it is notified that the data is MPEG data, notification processing of the details including whether it is MPEG 2 or MPEG4 is insufficient, which disadvantageously results in an improper data selection or data transmission request by the user on the client side.